Apparatus provided with a film frame judgement device

ABSTRACT

A camera includes a feeder for feeding a film having magnetic recording portions, a reader for magnetically scanning magnetic recording portions to generate scan signals, and a judger for judging whether or not a magnetic recording portion has been recorded with magnetic data by comparing scan signals with a threshold value, and a warning device for generating a warning when judgment of the judger is impossible. This apparatus can ensure more accurate judgment as to whether a signal picked up from each recording portion is a magnetic signal.

This is a divisional application of Ser. No. 08/801,392, filed Feb. 20,1997.

BACKGROUND OF THE INVENTION

This invention relates to an apparatus using a film, such as a camera,provided with a film frame judgment device for detecting a signal byrelatively scanning a recording portion of a fed film by an informationreading head and judging based on the detected signal whether an imageis recorded in a frame corresponding to the recording portion.

In recent years, the standardization of a novel photographing system hasbeen promoted. In a film used for this novel photographing system,strip-like magnetic recording tracks (hereinafter, referred to as"magnetic recording portion") are provided in parallel to the exposureareas of the respective frames at one side along the length of the film.Pieces of information concerning the photographing such as a date ofphotographing and an exposure value (hereinafter, referred to as "filmphotographing information") are magnetically recorded in the magneticrecording portions in correspondence with the frames.

In the film used for the novel photographing system, a light blockinglid is provided at a film outlet of a film cartridge as disclosed in,e.g., U.S. Pat. No. 5,347,334, and the film is completely contained inthe film cartridge. Further, a bar code plate by which the state of thecontained film (an unexposed film, an exposed film, a film which isexposed halfway (hereinafter, "a partly exposed film), a developed film,etc.) is detectable is integrally rotatably provided at one end of aspool. The state of the film can be distinguished by reading a bar codeon the bar code plate. Accordingly, even if the partly exposed film isrewound into the film cartridge and taken out of the camera, it can beloaded in the camera again to record images in unexposed frames.Further, a developed film can be stored by being contained in the filmcartridge.

In order to enable the image recording from the first unexposed frame ofthe partly exposed film reloaded in the camera, there has been proposeda film frame judgment device for detecting signals by scanning therespective magnetic recording portions of the loaded film by a magnetichead and judging whether the detected signal is a magnetic signal tojudge whether the frame corresponding to this magnetic recording portionis exposed.

FIG. 20 is a circuit construction diagram of a magnetic signal judgingcircuit of a prior art film frame judgment device.

A prior art magnetic signal judger 100 includes a magnetic head 101 forpicking up magnetic signals recorded in magnetic recording portions of afilm F, a magnetic signal processing circuit 102 for amplifying thepicked up signal (hereinafter, "pick-up signal") to a predeterminedspecified voltage, and a magnetic signal judging circuit 103 for judgingwhether the pick-up signal is a normal magnetic signal.

The magnetic signal judging circuit 103 takes only ac components V_(b)from an output signal V_(a) of the magnetic signal processing circuit102 by eliminating dc components V_(DC), generates a pulsating signalV_(c) (a signal corresponding to an envelope level of amplitudevariation of the ac components V_(b)) having low frequency components byrectifying and smoothing the ac components V_(b), and then judgeswhether the pick-up signal is a normal magnetic signal by comparing thepulsating signal V_(c) with a reference voltage V_(ref) input from acamera CPU 107.

A CR circuit constructed by a capacitor C1 and a resistor R1 at an inputside of the magnetic signal judging circuit 103 extracts the accomponents V_(b) from the output signal V_(a). A diode D after the CRcircuit rectifies the ac components V_(b). Further, a CR circuitconstructed by capacitors C2, C3 and resistors R2, R3 smoothes therectified ac components V_(b) and generates the pulsating signal V_(c).A comparator COMP compares the pulsating signal V_(c) with the referencevoltage V_(ref), and outputs a high level signal V_(d) representing thatthe pick-up signal is a normal magnetic signal when the pulsating signalV_(c) is equal to or above the reference voltage V_(ref) whileoutputting a low level signal V_(d) representing that the pick-up signalis not a normal magnetic signal when the pulsating signal is below thereference voltage V_(ref).

Whether or not the film photographing information is recorded in themagnetic recording portion of each frame of the film is made as follows.

Specifically, a feed roller 104 is rotated by a feed motor 105 with themagnetic head 101 pressed against the magnetic recording portion of thefilm F, thereby feeding the film F in a winding direction. The signal inthe magnetic recording portion is picked up by detecting voltagesinduced at the opposite ends of the magnetic head 101 by electromagneticinduction. The feeding speed and feeding direction of the film F arecontrolled by controlling the rotating speed and rotating direction ofthe feed motor 105 by a motor driver 106.

The signal picked up by the magnetic head 101 is amplified to thespecified voltage level by the magnetic signal processing circuit 102.Thereafter, in the magnetic signal judging circuit 103, the pulsatingsignal V_(C) corresponding to the envelope level of the amplitudevariation of the pick-up signal is generated; the judgment as to whetherthe pick-up signal is a normal magnetic signal representative of thefilm photographing information by comparing the pulsating signal V_(c)with the reference voltage V_(ref) ; and outputs a signal representativeof the judgment result (the output signal V_(d) of the comparator COMP)to the camera CPU 107.

The prior art magnetic signal judger 100 picks up the signal in themagnetic recording portion of the film F; extracts the pulsating signalV_(c) containing the low frequency components of the amplitude variationfrom the pick-up signal; and judges based only on the signal level ofthe pulsating signal V_(c) whether the pick-up signal is a normalmagnetic signal. Accordingly, an error judgment may be made for thepick-up signal due to the variation of the level of the magnetic signalresulting from a burst type noise coming from the outside, asignal-to-noise (S/N) characteristic of the magnetic recording portionand the variation of feeding speed of the film.

The magnetic layer of the magnetic recording portion of the film F has alower magnetic density as compared with acoustic and video magnetictapes. The S/N characteristic of the magnetic recording portion of thefilm F is not necessarily sufficient, and the film feeding system is notdesigned specially to read the magnetic signal recorded in the film F.Accordingly, in writing and reading the magnetic signal in and from themagnetic recording portion, the level of the magnetic signal may fall orlack as shown in FIG. 21, with the result that the magnetic signal maybe erroneously judged not to be a magnetic signal because of a lackingportion despite the fact that this signal is a magnetic signal. In FIG.21, the signal lacks in a portion A, where the level of the pick-upsignal V_(a) is a noise level.

For example, in the case that the above judgment is made near atelevision receiver, a scanning line noise (a noise resulting from avertical synchronization signal) of the television receiver may enterthe pick-up signal V_(a). In such a case, if the level of the pick-upsignal which is not a normal magnetic signal is largely changed by aburst type noise S_(B) resulting from the scanning line noise as shownin FIG. 22, this noise S_(B) may be erroneously judged to be a normalmagnetic signal.

It can be considered to avoid the maloperation of the magnetic signaljudger 100 by a circuit construction. However, since such a hardwaremeasure leads to a complicated circuit construction and a difficultcircuit design, it cannot be adopted because it is not necessarilyeffective in terms of a production cost.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an apparatus whichhas overcome the problems residing in the prior art.

It is another object of the present invention to provide an apparatusprovided with a film frame judgment device which can accurately judgewhether a signal picked up from each recording portion is a magneticsignal.

According to an aspect of the present invention, an apparatuscomprising: a feeder which feeds a film having a magnetic recordingportion; a reader which magnetically scans the magnetic recordingportion to generate scan signals; and a judger which executes a firstcomparison and a second comparison to make judgment as to which offirst, second, and third cases. The first case is one that the magneticrecording portion has been recorded with magnetic data; the second caseis one that the magnetic recording portion has not been recorded withmagnetic data; and the third case is one that the first and second casescannot be discriminated. The first comparison compares a scan signalfrom each of a plurality of blocks of the magnetic recording portionwith a first predetermined level. The second comparison compares a scansignal from each of the plurality of blocks of the magnetic recordingportion with a second predetermined level, the second predeterminedlevel being lower than the first predetermined level. The firstcomparison is given higher priority than the second comparison.

The judger may preferably make a judgment of: the first case when scansignals are in a first condition of being above the first predeterminedlevel over a specified number of continuous blocks; the third case whenscan signals are in a second condition of being below the firstpredetermined level and above the second predetermined level over aspecified number of continuous blocks; and the second case when scansignals are in the other condition.

The first predetermined level may be a threshold value for judgingwhether scan signals are in connection with magnetic data. The secondpredetermined level may be a threshold value for judging whether scansignals are in connection with noise.

It may be appreciated that the film apparatus is a camera.

According to another aspect of the present invention, a film apparatuscomprising: a feeder which feeds a film having a non-magnetic recordingportion and a magnetic recording portion; a reader which magneticallyscans the non-magnetic recording portion and the magnetic recordingportion to generate scan signals, scanning of the non-magnetic recordingportion being held for a predetermined period of 20 milliseconds ormore; and a judger which makes a threshold value based on scan signalsfrom the non-magnetic recording portion and judges whether or not themagnetic recording portion has been recorded with magnetic data bycomparing scan signals with the threshold value.

The threshold value may be made based on an average of scan signals fromthe non-magnetic recording portion.

The threshold value may be made based on an average of scan signals fromdivisions of the non-magnetic recording portion except maximum andminimum scan signals.

The threshold value may be made based on a median of scan signals fromdivisions of the non-magnetic recording portion.

According to still another aspect of the present invention, a filmapparatus comprising: a feeder which feeds a film having a magneticrecording portion; a reader which magnetically scans the magneticrecording portion to generate scan signals; and a judger which judgeswhether or not the magnetic recording portion has been recorded withmagnetic data by comparing scan signals with a threshold value; and awarning provider which provides a warning when judgment of the judger isimpossible.

It may be preferable that the warning provider activates rewinding ofthe film.

These and other objects, features and advantages of the presentinvention will become more apparent upon a reading of the followingdetailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic construction diagram of a camera embodying thepresent invention provided with a film frame judgment device;

FIG. 2 is a diagram showing a magnetic recording portion provided in afilm;

FIG. 3 is a diagram showing an exemplary waveform of a bit signal Pbrepresenting a film photographing information;

FIG. 4 is a block diagram of a control system of the film frame judgmentdevice;

FIG. 5 is a block diagram showing an internal construction of a filmframe judgment device;

FIG. 6 is a diagram showing one exemplary circuit construction of amagnetic signal writing circuit;

FIG. 7 is a diagram showing another exemplary circuit construction ofthe magnetic signal writing circuit;

FIG. 8 is a waveform chart showing an exemplary noise detection signal;

FIG. 9 is a waveform chart showing an exemplary detecting signal when amagnetic signal having a low level is detected;

FIGS. 10 to 13 are a flowchart showing a control sequence of a filmframe judgment processing;

FIG. 14 is a waveform chart showing an average value calculation overone block length of a detection signal of noise;

FIG. 15 is a waveform chart showing a rectification integration over oneblock length of the detection signal of noise;

FIG. 16 is a graph showing a noise level calculation for the framejudgment;

FIG. 17 is a graph showing an exemplary variation of the rectificationintegral value of a detection signal calculated by the block;

FIG. 18 is a flowchart showing a modification of Step #10 of the controlsequence;

FIG. 19 is a flowchart showing another modification of Step #10 of thecontrol sequence;

FIG. 20 is a circuit construction diagram of a magnetic signal judger ina prior art film frame judgment device;

FIG. 21 is a waveform chart of a magnetic signal in which a filmphotographing information is lacking; and

FIG. 22 is a waveform chart of a magnetic signal influenced by a bursttype noise.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION

FIG. 1 is a schematic construction diagram of a camera embodying thepresent invention provided with a film frame judgment device.

In FIG. 1, a camera 1 is provided with a film frame judgment device. Inthis figure, identified by 30 is a film cartridge loaded in a cartridgechamber provided at one end portion of the camera main body, by 40 atake-up spool rotatably provided in a film take-up chamber at the otherend portion of the camera main body, and by 50 an exposure frameprovided between the cartridge chamber and the film take-up chamber andbehind a taking lens. The exposure frame 50 acts as a guide plate forfeeding a film F pulled out of the film cartridge 30 to the film take-upchamber and is provided in its substantially center portion with arectangular exposure aperture 51 of specified size (e.g., about 17 mm(height)×about 30 mm (width)) so as to restrict a projection of anobject image to the film F.

The film F includes a plurality of frames Fa along its length and areformed along one edge portion (upper edge portion in FIG. 1) with pairsof perforations Fb, Fb' indicative of exposure areas of the frames Fa incorrespondence with the frames Fa. The perforations Fb, Fb' indicatefront and rear end positions of the corresponding frame Fa with respectto a film winding direction, respectively, and are formed in specifiedpositions at the opposite ends of each frame Fa.

Strip-like magnetic recording portions Fc having a specified length L(e.g. 22 mm) are provided in correspondence with the respective framesFa along the other edge portion (lower edge portion in FIG. 1) of thefilm F. Each magnetic recording portion Fc is adapted to magneticallyrecord a film photographing information (including photographingconditions such as a date of photographing, an exposure value and anexposure correction, a framing information, and a print size information(standard/panorama)) concerning the photographing of the correspondingframe Fa.

The film photographing information is written in the magnetic recordingportion Fc by a magnetic head 4 to be described later during filmwinding after an image is recorded in the corresponding frame Fa.

The respective pieces of information constituting the film photographinginformation are expressed in binary data including specified number ofdigits. Data of "0" and "1" constituting this binary data are written inthe magnetic recording portion Fc in the form of a bit signal Pb havinga waveform as shown in FIG. 3.

The bit signal Pb shown in FIG. 3 is such that two kinds of pulsesignals having different duty ratios (t_(y) /t_(x)) are allotted to thedata "0" and "1". Although a cycle t_(x) of the bit signal Pb changesdepending on a feeding speed v of the film F, since the duty ratios donot change, the content, i.e. "0" or "1" of each bit signal Pb can bejudged based on its duty ratio.

A signal representing the film photographing information (hereinafter,"Ix-signal") which is to be written in the magnetic recording portion Fcis specified to consist of at least 248 bits. Since the length of themagnetic recording portion is 22 mm, a minimum bit density Db is 11.3bits/mm (=248 bits/22 mm). Any writing condition which satisfies theabove writing condition can be selectively set in the camera.

The feeding speed v of the film F when the film photographinginformation is written is set in a range of, e.g. 50 mm/s to 200 mm/s. Aminimum frequency f_(MIN) of the Ix-signal picked up from the magneticrecording portion Fc is set at 563.6 Hz (=50 mm/s×11.3 bits/mm).

Referring back to FIG. 1, the film frame judgment device includesphotointerrupters 2, 3 for detecting the perforations Fb, Fb', amagnetic head 4 for writing and reading the film information in and fromthe magnetic recording portion Fc, a head controller 5 for controllingthe driving of the magnetic head 4, a motor 6 as a drive source forfeeding the film F, a motor driver 7 for controlling the driving of themotor 6, a pulse plate 8 and a photoreflector 9 for monitoring arotation amount of the motor 6, a torque transmission mechanism 10, anda controller 11. The torque transmission mechanism 10 switchinglytransmits a torque of the motor 6 to a driving axis 12 fitted into thespool of the film cartridge 30 and a drive gear 13 of the take-up spool40. The controller 11 controls the driving of each element to write andread the film photographing information and to make a judgment for eachframe.

The photointerrupter 2 (hereinafter, "PI 2") is arranged in a positionin the vicinity of an upper corner portion of the exposure aperture 51at the side to the take-up spool 40 where it faces a movement path ofthe perforations Fb, Fb'. The photointerrupter 3 (hereinafter, "PI 3")is arranged in a position in the vicinity of an upper corner portion ofthe exposure aperture 51 at the side to the cartridge chamber where itfaces the movement path of the perforations Fb, Fb'.

The PI 2 is adapted to position the exposure area of each frame Fa withrespect to the exposure aperture 51 and to detect start timings of thewriting and reading of the film photographing information in and fromthe magnetic recording portion Fc of each frame. More specifically, whenthe film F is fed until the perforation Fb is detected by the PI 2, theexposure area of this frame Fa coincides with the exposure aperture 51.Further, the front end position of the magnetic recording portion Fc isdisplaced from the perforation Fb by a specified distance d as shown inFIG. 2. The writing and reading of the film photographing information inand from the magnetic recording portion Fc are performed by controllingthe driving of the magnetic head 4 upon feeding the film F by thedistance d from the detection position of the perforation Fb by the PI2. The PI 2 detects the perforations Fb, Fb' based on a change in thedetection signal resulting from the fact that the interruption of alight path is released by the holes.

The PI 3 detects the leading end of the film F coming out of the filmoutlet of the film cartridge 30. The PI 3 detects the leading end of thefilm F based on a change in the detection signal resulting from the factthat a light path is interrupted by the film F. The detection signals ofthe PIs 2 and 3 are input to the controller 11.

The leading end of the film F is detected by the PI 3 to securely detecta noise signal by the magnetic head 4 and to set judgment thresholdvalues when judging based on the presence or absence of the Ix-signalwhether each frame is exposed or unexposed during the loading of thefilm F. More specifically, when the magnetic head 4 is driven upon thedetection of the leading end of the film F by the PI 3, the film F hasnot yet reached the magnetic head 4. Accordingly, a signal (noisesignal) in an area other than the magnetic recording portions Fc cansecurely be detected. The setting of the judgment threshold value isdescribed in detail later.

In order to have a small size, the magnetic head 4 is constructed by ahead of core sharing type in which a write coil 4A and a read coil 4Bare wound around a single ring-shaped core 4C (see FIG. 4). The headcontroller 5 includes a magnetic signal writing circuit 5A connectedwith the write coil 4A and a magnetic signal reading circuit 5Bconnected with the read coil 4B (see FIG. 4).

The magnetic signal writing circuit 5A converts a direct current into analternating current based on the Ix-signal (bit signal Pb) whichrepresents the film photographing information and is output from thecontroller 11 and supplies the obtained alternating current to the writecoil 4A. When the alternating current flows in the write coil 4A, afluctuating magnetic field corresponding to the magnetic signal isgenerated at a gap of the magnetic head 4. The film photographinginformation is recorded by magnetizing the magnetic recording portion Fcby this fluctuating magnetic field.

The magnetic signal reading circuit 5B is mainly constructed by anamplifier and is adapted to amplify the signal detected by the magnetichead 4 by superimposing it on a specified dc bias level and to outputthe amplified signal. Specifically, the circuit 5B has an output voltagerange of, e.g. 0 to 5 V, and amplifies and outputs the signal detectedby the magnetic head 4 into a signal having 2.5 V as a center point andan amplitude of 2.5 V or smaller.

The motor 6 includes an electric motor such as a stepping motor. Themotor driver 9 generates a control signal (e.g., a pulse train signal)to the motor 6 and outputs it to the motor 6 so as to control therotating speed, rotation amount, activation/deactivation and the like ofthe motor 6.

The pulse plate 8 and the photoreflector 9 construct a pulse generator14 (see FIG. 4) for generating a pulse train signal to detect therotation amount, the rotating speed and the like of the motor 6. Thepulse plate 8 is a disk formed at its periphery with strips or grooveshaving a shape of gear teeth which are circumferentially arranged atspecified intervals. By detecting the stripes or grooves by thephotoreflector 9, a pulse train signal of a cycle corresponding to therotating speed of the pulse plate 8 is generated. This pulse trainsignal is output to the controller 11.

The torque transmission mechanism 10 includes a speed reducing/drivetransmitting portion constructed by a combination of planetary geardevices and a drive direction switching portion for switching theconnection of gear trains by a cam, and switches the transmissiondirection of the torque of the motor 6 by switching the position of thecam. The camera is provided with three torque transmission modes: a windmode, a rewind mode and a thrust mode. In the wind mode, the torque ofthe motor 6 is transmitted to the drive gear 13 via the torquetransmission mechanism 10, with the result that the film F is fed in thewinding direction by the rotation of the take-up spool 40.

In the rewind mode, the torque of the motor 6 is transmitted to the fork12 and the spool to which the fork 12 is fitted via the torquetransmission mechanism 10, with the result that the film F is fed in therewinding direction by the rotation of the spool of the film cartridge30. The thrust mode is a drive mode for the film loading. In this mode,the torque of the motor 6 is transmitted to the fork 12 and the drivegear 13 via the torque transmission mechanism 10, with the result thatthe film F is thrusted out of the film cartridge 30 by the rotation ofthe spool of the film cartridge 30. After the film F is nipped by thetake-up spool 40, the film F is fed in the winding direction until theexposure area of the leading frame Fa reaches the exposure aperture 51by the rotation of the spool and the take-up spool 40.

FIG. 4 is a block diagram of a control system of the film frame judgmentdevice 1, and FIG. 5 is a block diagram showing the internalconstruction of a film frame judgment device. In FIG. 4, the sameelements as those shown in FIG. 1 are identified by the same referencenumerals.

The controller 11 is provided with a film feed amount detector 15, amotor controller 16, a write/read controller 17, a write data generator18, an analog-to-digital (A/D) converter 19 and a frame judging section20.

The film feed amount detector 15 detects the feeding speed and the feedamount of the film F based on the pulse train signal input from thepulse generator 14. Specifically, the detector 15 detects a pulseduration τ (sec.) of the pulse train signal, and calculates the feedingspeed v from this pulse duration τ and a pulse number N_(P) per rotationof the motor 6. Assuming that the film F is fed by S (mm) by one turn ofthe motor 6, the feeding speed v is calculated by S/(τ×N_(P)). Thedetector 15 also calculates the feed amount D of the film F by adding apulse number N. The feed amount D is calculated by N·S/N_(P). Thedetection data of the detector 15 are input to the write/readcontroller.

The motor controller 16 controls the drive and the driving direction ofthe motor 6. The motor controller 16 outputs a drive control signal tothe motor driver 7 in accordance with a control signal from thewrite/read controller 17.

The write/read controller 17 controls the writing and reading of thefilm photographing information. The write/read controller 17 controlsthe feed of the film F via the motor controller 16 so as to relativelymove the magnetic head 4 with respect to the film F, that is, so as toscan the film F. Further, as described later, during the film loading,the write/read controller 17 controls the drive of the frame judgingsection 20 to cause it to make a judgment for each frame (whether or notthe frame is unexposed) based on the signal detected from the magneticrecording portion Fc.

The write data generator 18 generates a write data used to drive themagnetic head 4 based on the film photographing information representedby the bit signal Pb. The magnetic signal writing circuit 5A isconstructed by an inverter circuit including four switching devices Q1to Q4 as shown in FIG. 6. In this embodiment, the switching devices Q1,Q2 are pnp-type transistors, whereas the switching devices Q3, Q4 arenpn-type transistors.

A series circuit formed by the transistors Q1, Q3 and a series circuitformed by the transistors Q2, Q4 are connected in parallel, and thewrite coil 4A is connected between a point of connection between thetransistors Q1 and Q3 and a point of connection between the transistorsQ2 and Q4. Further, the emitters of the transistors Q3, Q4 are groundedvia a resistor r1, whereas the emitters of the transistors Q1, Q2 areconnected with a dc power source Vcc via a switching circuit 21constructed by switching devices Q5 and Q6.

The switching circuit 21 is adapted to completely interrupt a dc supplypath from the dc power source Vcc to the magnetic signal writing circuit5A when the magnetic head 4 is used as a reading head, therebypreventing a mutual induction action of the write coil 4A and the readcoil 4B. The switching devices Q5, Q6 are a pnp-type transistor and annpn-type transistor, respectively. The emitter of the transistor Q5 isconnected with the dc power source Vcc, and the connector thereof isconnected with the emitters of the transistors Q1, Q2. The collector ofthe transistor Q6 is connected with the base of the transistor Q5 via aresistor r2, and the emitter thereof is grounded. To the base of thetransistor Q6 is input a control signal S_(C) for turning the transistorQ6 on and off via a resistor r3. The control signal S_(C) is input tothe magnetic signal writing circuit 5A from the write/read controller17.

Upon the receipt of the control signal S_(C) of high level, thetransistor Q6 is turned on, and the base of the transistor Q5 becomeslow level, thereby turning on the transistor Q5 (conductive state). Onthe other hand, upon the receipt of the control signal S_(C) of lowlevel, the transistor Q6 is turned off, and the base of the transistorQ5 becomes high level, thereby turning off the transistor Q5(nonconductive state).

Although the switching circuit 21 is provided between the dc powersource Vcc and the transistors Q1, Q2 in FIG. 6, a switching circuit 21'may be provided between the resistor r1 and the ground as shown in FIG.7. In FIG. 7, the switching circuit 21' is constructed by an npn-typetransistor Q7, and the control signal S_(C) is input to the base of thetransistor Q7 via a resistor r4. In this case as well, upon the receiptof the control signal S_(C) of high level, the transistor Q7 is turnedon (conductive state). Upon the receipt of the control signal S_(C) oflow level, the transistor Q7 is turned off (nonconductive state).

The write data is input to the bases of the transistors Q1 to Q4 viabuffer amplifiers BA1 to BA4. The transistors Q1, Q2 are turned on uponthe receipt of a low level signal, whereas the transistors Q3, Q4 areturned on upon the receipt of a high level signal. Accordingly, if thewrite data is a 4-bit data (q1, q2, q3, q4) and "1" and "0" denote ahigh level signal and a low level signal, respectively, a write data (1,1, 0, 0) is output from the write data generator 18 when the writing isnot performed. Further, when the film photographing information is to bewritten, a write data (1, 0, 1, 0) is output from the write datagenerator 18 if there is a current ia flowing downward of the write coil4A in FIG. 6. Conversely, a write data (0, 1, 0, 1) is output from thewrite data generator 18 if there is a current ib (=-ia) flowing upwardof the write coil 4A in FIG. 6.

The write data generator 18 outputs the write data to the magneticsignal writing circuit 5A at a specified timing when the information isto be written in accordance with the control signal from the write/readcontroller 17.

The A/D converter 19 converts an analog signal S_(P) input from themagnetic signal reading circuit 5B into a digital signal S_(P). In thisembodiment, the A/D converter 19 converts the analog signal S_(P) into a8-bit digital data. Specifically, the A/D converter 19 applies asampling to the signal S_(P) in a specified cycle in accordance with asampling clock SCK input from a block length setter 202; converts thelevel of each sampling signal from an analog value into a digital value;and outputs the thus obtained digital data to the frame judging section20 and an unillustrated information decoder for decoding the filmphotographing information from the magnetic signal.

The frame judging section 20 judges based on the level of the signalS_(P) detected from the magnetic recording portion Fc whether the signalS_(P) is an Ix-signal, and also judges based on the above judgmentresult whether the frame Fa corresponding to the magnetic recordingportion Fc is unexposed or not.

The frame judging section 20 includes a threshold level calculator 201,the block length setter 202, a magnetic signal detector 203 and anunexposed frame judger 204.

The threshold level calculator 201 calculates threshold levels V_(HL),V_(HH) used to judge whether the signal S_(P) detected in the magneticrecording portion Fc is an Ix-signal based on a signal S_(P) ' detectedwhen the magnetic head 4 is located in a position outside the magneticrecording portion Fc (i.e. noise signal S_(P) '). The threshold levelV_(HL) is a level used to judge whether the signal S_(P) is a noisesignal, whereas the threshold level V_(HH) (>V_(HL)) is a level used tojudge whether the signal S_(P) is an Ix-signal. The data on thethreshold levels V_(HL), V_(HH) are output to the unexposed frame judger204.

The threshold level calculator 201 includes, as shown in FIG. 5, anaverage value calculator 201A, a rectification integrator 201B, a noiselevel calculator 201C, a threshold level setter 201D, and a memory 201E.As described later, the frame judgment is made by dividing the magneticrecording portion Fc into a plurality of blocks and generating ajudgment signal based on the signal S_(P) detected block by block. Thememory 201E is adapted to store the digital signal S_(P) ' input fromthe A/D converter 19 for each block length. The average value calculator201A calculates an average level V_(NAVE) of the digital signal S_(P) 'for each block. The rectification integrator 201B applies a full waverectification to the digital signal S_(P) ' on the basis of the averagelevel V_(NAVE), and integrates this rectification signal. The noiselevel calculator 201C calculates a noise level K by averaging integralvalues S_(N) calculated for a plurality of blocks (=ΣS_(N) /n: n=thenumber of blocks).

The rectification integral value of the detection signal is used for thefollowing reason. According to a method for comparing the levels of thedetection signal, the detection signal of the Ix-signal may erroneouslybe judged to be a noise in the case that the level of the detectionsignal of the Ix-signal is substantially as low as a noise level asshown in FIGS. 8 and 9. However, if the rectification integral value isused, the level of the detection signal of the Ix-signal is considerablyhigher than that of the detection signal of the noise. Accordingly, anerror judgment can securely be prevented.

FIG. 8 is a waveform chart showing an exemplary detection signal ofnoise, and FIG. 9 is a waveform chart showing an exemplary detectionsignal in the case that the Ix-signal having a low level is detected.Since a fluctuating cycle is higher than a noise even if the maximumlevel of the detection signal of the Ix-signal is approximately equal tothe noise level, the detection signal of the Ix-signal is higher thanthat of the noise after the rectification integration.

The integral values of the plurality of blocks are averaged to preventthe noise level K from abnormally increasing when an unexpected externalnoise accidentally enters. In this embodiment, particularly in order toprevent a level abnormality caused by an unexpected external noiseresulting from a commercial frequency (60 Hz/50 Hz), the integral valuesof five blocks are averaged to obtain an average value over a durationof at least 20 ms or longer.

For the similar reason, the integral value of the plurality of blocksexcept the maximum and minimum values may be averaged; the maximum andminimum integral values may be averaged; or a median may be used as anaverage value.

The threshold level setter 201D is adapted to set the threshold dataV_(HL) (=a1×K), V_(HH) (=a2×K) by multiplying the noise level K byspecified coefficients a1, a2, respectively. The lower the level of thesignal S_(P) detected in the magnetic recording portion Fc may be, themore difficult it is to judge whether the detection signal representsthe noise or the Ix-signal. In order to make an accurate judgment evenin such a case, two kinds of threshold data V_(HL), V_(HH) are set. Thecoefficients a1, a2 are empirically set in view of the characteristicsof the magnetic head 4, the level of the external noise, and otherfactors. In this embodiment, a1=1.75 and a2=2.5.

The block length setter 202 is adapted to divide the magnetic recordingportion Fc into a plurality of blocks. The setter 202 has a built-inreference clock; generates the sampling clock SCK in accordance with thereference clock and outputs it to the A/D converter 19; and sets a blocklength, i.e. a detection time T of the detection signal S_(P) inaccordance with the sampling clock SCK. In this embodiment, thedetection time T for one block is set at 4 ms, and the detection signalSP is A/D converted every 40 μs so that 100 digital data V(0) to V(99)are read for each block.

The magnetic signal detector 203 generates a data used to compare thethreshold data V_(HL), V_(HH) based on the signal S_(P) detected byscanning the magnetic recording portion Fc by the magnetic head 4. Thisdata is also generated block by block and output to the unexposed framejudger 204.

The magnetic signal detector 203 includes, as shown in FIG. 6, anaverage value calculator 203A, a rectification integrator 203B, a signallevel calculator 203C and a memory 203E. The average value calculator203A, the rectification integrator 203B and the memory 203E function inthe corresponding manner as the average value calculator 201A, therectification integrator 201B and the memory 201E of the threshold levelcalculator 201. More specifically, the memory 203E is adapted to storethe digital signal S_(P) (signal obtained by scanning the magneticrecording portion Fc) input from the A/D converter 19 for each blocklength. The average value calculator 203A calculates an average levelV_(SAVE) of the digital signal S_(P) for each block. The rectificationintegrator 203B applies a full wave rectification to the digital signalS_(P) on the basis of the average level V_(SAVE) and integrates thisrectification signal.

The unexposed frame judger 204 classifies the signal levels of therespective blocks into three levels (S_(S) ≦V_(HL), V_(HL) <S_(S),V_(HH) <S_(S)) by comparing each integral value S_(S) based on thesignal S_(P) obtained by scanning the magnetic recording portion Fc foreach block with the threshold data V_(HL), V_(HH), and judges based onthis classification results whether the frame Fa corresponding to thismagnetic recording portion Fc is an unexposed frame or an exposed frameor cannot be judged. In this embodiment, if there are three or moreconsecutive blocks of V_(HH) <S_(S), the frame Fa is judged to be anexposed frame. If there are three or more consecutive blocks of V_(HL)<S_(S) although there are no three consecutive blocks of V_(HL) <S_(S),no judgment is possible for the frame Fa. Unless otherwise, the frame Fais judged to be an unexposed frame.

The number of the consecutive blocks is set at three or more for thefollowing reason. For example, concerning a noise resulting from avertical synchronization signal of a television, a noise resulting froma vertical synchronization signal of one cycle is normally frequentlycounted for the integral value S_(S). With such an unexpected noisehaving a relatively high level, it is considered that two consecutiveblocks of V_(HH) <S_(S) may exist, but that three or more of suchconsecutive blocks are highly unlikely to exist. It should be noted thatthe number of consecutive blocks is not limited to three, but may befour or more.

Next, the film frame judgment and the film photographing informationwrite control are specifically described with reference to a flowchartshown in FIGS. 10 to 13.

The frame judgment is made during the film loading performed when thefilm cartridge 30 is loaded in the film chamber in order to feed thefilm F until the first unexposed frame reaches the specified imagerecording position, that is, the exposure aperture 51, in the case thata partly exposed film is loaded. Further, the film photographinginformation is written while the film F is fed by one frame after anexposure is made to the frame. The flowchart shown in FIGS. 10 to 13 isa control sequence of the film loading including the frame judgment andthe photographing following thereafter.

Concerning the film loading, when the film cartridge 30 is loaded in thefilm chamber, the torque transmission mechanism 10 is set in the thrustmode for the film loading, and the film F is thrusted out of the filmcartridge 30 by rotating the fork 12 by the torque of the motor 6 (Step#1). The control signal S_(C) of low level is then output to themagnetic signal writing circuit 5A and power application to the magneticsignal writing circuit 5A is cut off (Step #2). Subsequently, when theleading end of the thrusted out film F is detected by the PI 3 (YES inStep #3), a count value m of a counter for counting the number of blocksis set to "0" (Step #4), and the signal S_(P) ' detected by the readcoil 4B of the magnetic head 4 is read for five block lengths (read time5T=20 ms) (a loop of Steps #5 to #9). During the read time 5T, thedetection signal S_(P) ' is the detection signal of noise since the filmF has not yet reached the magnetic head 4.

The detection signal S_(P) ' is then A/D converted into digital dataV_(N) (i) in sampling cycle ts=40 μs by the A/D converter 19 and isstored in the memory 201E per block length (one block length T, thenumber of data i=0 to 99). The detection signal S_(P) ' is alsoconverted into a rectification integral value S_(N) (m)(m=0 to 4) by theaverage calculator 201B and the rectification integrator 201B (Steps #5to #7).

The rectification integral value S_(N) (m) of each block is calculatedas follows. The average level V_(NAVE) (m)(=ΣV_(N) (i)/100, i=0 to 99,m=0 to 4) for each block length T of the detection signal S_(P) ' iscalculated as shown in FIG. 14 (Step #6). Further, as shown in FIG. 15,after a full wave rectification is applied to the detection signal S_(P)' using the average level V_(NAVE) as a reference level, the signallevel is integrated (corresponding to a hatched area of FIG. 15) toobtain the rectification integral value S_(N) (m) of the block. Theabove rectification integration is performed by calculating absolutevalues of differences |V_(N) (i)-V_(NAVE) (m)| between the data V_(N)(i) read from the memory 201E and the average level V_(NAVE) (m) by therectification integrator 201B and adding these absolute values (Σ|V_(N)(i)-V_(NAVE) (m)|, i=0 to 99, m=0 to 4).

When the calculation of the rectification integral values S_(N) (0) toS_(N) (4) of five blocks is completed (YES in Step #9), the noise levelcalculator 201C calculates an average value K of these rectificationintegral values (ΣS_(N) (m)/5, m=0 to 4) as a noise level as shown inFIG. 16 (Step #10), and the threshold level setter 201D sets thethreshold values V_(HL), V_(HH) by multiplying the average value K bythe coefficients a1, a2, respectively (Step #11). FIG. 16 is a bar graphshowing the rectification integral values S_(N) (0) to S_(N) (4)corresponding to periods T0 to T1, T1 to T2, . . . , T4 to T5, and thelevel K is an average value of the rectification integral values S_(N)(0) to S_(N) (4).

It may be appreciated to average those of the rectification integralvalues S_(N) (0) to S_(N) (4) except maximum and minimum values as shownin FIG. 18, instead of the averaging of all the rectification integralvalues S_(N) (0) to S_(N) (4). Specifically, in Step #10-1, therectification integral values S_(N) (0) to S_(N) (4) of the five blocksare sorted in the order of higher value. A result of the sorting isrepresented as an arrangement of Sx(0)>Sx(1)>Sx(2)>Sx(3)>Sx(4). In Step#10-2, the maximum and minimum values Sx(0) to Sx(4) are removed and anaverage value K of the remaining values Sx(1) to Sx(3) is calculated asa noise level: K(=Sx(1)+Sx(2)+Sx(3)/3).

Further, it may be appreciated to use a median as an average value asshown in FIG. 19, instead of the averaging of all the rectificationintegral values S_(N) (0) to S_(N) (4). Specifically, in Step #10-1',the rectification integral values S_(N) (0) to S_(N) (4) of the fiveblocks are sorted in the order of higher value similarly to Step #10-1to obtain an arrangement of Sx(0)>Sx(1)>Sx(2)>Sx(3)>Sx(4). In Step#10-2', the median value Sx(2) is used as a noise level.

Subsequently, when the front end position of the magnetic recordingportion Fc (the front end position of the magnetic track) correspondingto the leading frame of the frame Fa is detected after the film F is fedby a specified distance (distance d) in accordance with the detectionsignal of the perforation Fb by the PI 2 (Step #12), a count value X ofa counter for counting the number of consecutive blocks having a levelin excess of the threshold level V_(HH) and a count value Y of a counterfor counting the number of consecutive blocks having a level in excessof the threshold level V_(HL) in the signal S_(p) detected by scanningthe magnetic recording portion Fc by the magnetic head 4 are both set to"0", and a flag FLGA representing that the judgment is impossible isreset to "0" (Step #13).

Subsequently, the signal S_(p) detected via the read coil 4B of themagnetic head 4 and the magnetic signal reading circuit 5B are stored inthe memory 203E after being A/D converted for each block length (oneblock length T, number of data i=0 to 99) by the A/D converter 19 (Step#14). Then, the rectification integral values S_(S) of the respectiveblocks are calculated by the calculation similar to the one for thedetection signal S_(P) ' of noise (Steps #15, #16).

More specifically, the average level V_(SAVE) (=ΣV_(S) (i)/100, i=0 to99) is calculated by the average value calculator 203A (Step #15).Further, the rectification integrator 203B reads the respective dataS_(S) (i) from the memory 203E, and calculates the rectificationintegral value S_(S) by adding the absolute values of differences |V_(S)(i)-V_(SAVE) | between the data V_(S) (i) read from the memory 203E andthe average level V_(SAVE) (Step #16).

Subsequently, the unexposed frame judger 204 compares the rectificationintegral value S_(S) with the threshold levels V_(HH) (Step #17) andV_(HL) (Step #20) to classify in which ranges of S_(S) ≦V_(HL), V_(HL)<S_(S), V_(HH) <S_(S) the rectification integral value S_(S) of thatblock falls. Depending on the classification results, the count value Xof the consecutive blocks of V_(HH) <S_(S) is changed (Step #18 or #19)or reset to "0" (Step #19), and the count value Y of the consecutiveblocks of V_(HL) <S_(S) is changed (Step #21 or #22). More specifically,if V_(HH) <S_(S) (YES in Step #17), the count value X is incremented by"1" (Step #18). If S_(S) ≦V_(HH) (NO in Step #17), the count value X isreset to "0" (Step #19). Further, if V_(HL) <S_(S) (YES in Step #20),the count value Y is incremented by "1" (Step #21). If S_(S) ≦V_(HL) (NOin Step #20), the count value Y is reset to "0" (Step #22).

It is then judged whether the count value X has reached "3", i.e. therehave been three consecutive blocks having a level in excess of thethreshold level V_(HH) (Step #23). If X=3 (YES in Step #23), Step #12follows upon the judgment that the frame corresponding to this magneticrecording portion Fc is an exposed frame, and the same frame judgment asabove is made for the next frame (Steps #12 to #23).

On the other hand, unless X=3 (NO in Step #23), it is judged whether thecount value Y has reached "3", i.e., there have been three consecutiveblocks having a level in excess of the threshold level V_(HL) althoughthere have been no three consecutive blocks having a level in excess ofV_(HH) (Step #24). If Y=3 (YES in Step #24), Step #26 follows after theflag FLGA is set to "1" (Step #25). Unless Y=3 (NO in Step #24), Step#26 directly follows.

FIG. 17 is a graph showing an exemplary variation of the rectificationintegral values S_(S) of the detection signal S_(P) calculated block byblock. Specifically, FIG. 17 is a bar graph showing the rectificationintegral values S_(S) (0), S_(S) (1), S_(S) (2), . . . S_(S) (5)corresponding to periods T0' to T1', T1' to T2', . . . T5' to T6'. Inthis example, since the rectification integral values S_(S) (3) to S_(S)(5) of the signals S_(P) continuously read by scanning the magneticrecording portion Fc are consecutively in excess of the threshold levelV_(HH), the frame Fa corresponding to this magnetic recording portion Fcis judged to be an exposed frame. On the other hand, if therectification integral value S_(S) (3) is: V_(HL) ≦S_(S) (3)<V_(HH), nothree consecutive rectification integral values are in excess of thethreshold level V_(HH), but three or more consecutive rectificationintegral values are in excess of the threshold level V_(HL) (S_(S) (1)to S_(S) (3)), no frame judgment is judged to be possible. If there areonly two consecutive blocks having a level in excess of the thresholdvalue V_(HL), the frame corresponding to this magnetic recording portionFc is judged to be an unexposed frame upon the judgment that theIx-signal is not recorded therein.

Referring back to FIG. 12, it is judged whether the frame judgment hasbeen made for all blocks of the magnetic recording portion Fc (Step#26). If the frame judgment has not yet been made for all blocks of themagnetic recording portion Fc (NO in Step #26), this routine returns toStep #14 and the classification of the rectification integral value andthe frame judgment are performed for the next block (Steps #14 to #26).

Upon the completion of the frame judgment for all blocks of the magneticrecording portion Fc (YES in Step #26), it is judged whether the flagFLGA is set at "1" (Step #27). If the flag FLGA is set at "1" (YES inStep #27), the frame judgment is judged to be impossible (Step #28).Then, the drive mode for the torque transmission mechanism 10 is set tothe film rewind mode (Step #29) and the film F is rewound by rotatingthe fork 12 in the reverse direction by the torque of the motor 6 (Step#30). Upon the completion of the rewinding (YES in Step #30), a warning"Frame Judgment Impossible" is displayed in a display device provided onthe camera main body (Step #31). When the film cartridge 30 is ejected(YES in Step #32), the film loading and the frame judgment arecompleted.

On the other hand, unless the flag FLGA is set at "1" (NO in Step #27),the frame Fa corresponding to the magnetic recording portion Fc isjudged to be an unexposed frame (Step #33) and the film F is rewound byone frame to position the exposure area of the frame Fa with respect tothe exposure aperture 51. Specifically, the drive mode for the torquetransmission mechanism 10 is set to the film rewind mode, and the film Fis rewound by rotating the fork 12 in the reverse direction by thetorque of the motor 6 until the perforation Fb representing the frontend position of this frame Fa is detected by the PI 2 (Steps #34, #35).Consequently, the film loading and the frame judgment are completed.

Subsequently, when the photographing is performed by pressing anunillustrated release switch S2 (YES in Step #36), an image is recordedin the leading unexposed frame in the image recording position (Step#37). Thereafter, the drive mode for the torque transmission mechanism10 is set to the film wind mode to start the feed of the film F by oneframe by driving the motor 6 (Step #38). Simultaneously, the controlsignal S_(c) of high level is output to the magnetic signal writingcircuit 5A, and power application to the circuit 5A is permitted (Step#39). This is because the film photographing information correspondingto the frame Fa to which an exposure was made is written while the filmF is fed by one frame.

Subsequently, when the front end position of the magnetic recordingportion Fc is detected by feeding the film F by a specified amount (Step#40), the write data is output from the write data generator 18 to themagnetic signal writing circuit 5A, and the film photographinginformation is recorded in this magnetic recording portion Fc (Step#41). When the perforation Fb representing the front end position of thenext frame Fa is detected by the PI 2 (YES in Step #42), the motor 6 isstopped to stop the feed of the film F (Step #43). Then, powerapplication to the magnetic signal writing circuit 5A is interrupted(Step #44) and it is judged whether an exposure has been made to thelast frame (Step #45). Unless an exposure has been made to the lastframe (NO in Step #45), Step #36 follows and the film photographinginformation is recorded in the magnetic recording portion Fc every timean exposure is made to the frame by repeating the above operations (aloop of Steps #36 to #45).

When all frames are exposed (YES in Step #45), the drive mode for thetorque transmission mechanism 10 is set to the film rewind mode and thefilm F is rewound by rotating the fork 12 in the reverse direction bythe torque of the motor 6 (Steps #46, #47). Upon the completion of therewinding (YES in Step #47), the recording of the film photographinginformation in association with the photographing operation is completedby ejecting the film cartridge 30 (YES in Step #48).

As described above, a film having recording portions in correspondenceto the respective frames for recording information concerning anexposure made to the frames is fed by the film feeder. The film framejudgment device judges, based on the signal detected by relativelyscanning the recording portion by the information reader, whether anexposure can be made to the frame corresponding to this recordingportion.

Specifically, first and second threshold values for the judgment setbased on the signal detected in a scanning position of the informationreader outside the recording portions. The detection signal obtained byscanning the recording portion is converted into a rectificationintegration signal for each of a plurality of blocks, and then theserectification integration signals are compared with the first and secondthreshold values to classify the signals level of the respective blocksinto three ranges. Based on the classification result, the framecorresponding to this recording portion is judged to be an exposed framewhen there are a specified number or more consecutive blocks having anintegral value in excess of the second threshold value, and the judgmentis judged to be impossible when there are a specified number of moreconsecutive blocks having an integral value in excess of the firstthreshold value although there are no specified number or more blockshaving an integral value in excess of the second threshold value.

In this way, the frame corresponding to the magnetic recording portionis judged to be exposed or unexposed, or no judgment is judged to bepossible. Accordingly, even in the case that the level of the recordingsignal representing the recorded information is approximately as low asnoise level or in the case that a burst type noise is generated due to avertical synchronization signal of a television, the recording signalcan securely be detected without erroneously judging a noise as such,and whether each frame is exposed or not can accurately be judged.

Although the present invention has been fully described by way ofexample with reference to the accompanying drawings, it is to beunderstood that various changes and modifications will be apparent tothose skilled in the art. Therefore, unless otherwise such changes andmodifications depart from the scope of the present invention, theyshould be construed as being included therein.

What is claimed is:
 1. An apparatus comprising:a feeder which feeds afilm having a magnetic recording portion; a reader which magneticallyscans the magnetic recording portion to generate scan signals; and ajudger which executes a first comparison and a second comparison to makejudgment as to which of first, second, and third cases:the first casebeing that the magnetic recording portion has been recorded withmagnetic data the second case being that the magnetic recording portionhas not been recorded with magnetic data; and the third case being thatthe first and second cases cannot be discriminated; the first comparisoncomparing a scan signal from each of a plurality of blocks of themagnetic recording portion with a first predetermined level; the secondcomparison comparing a scan signal from each of the plurality of blocksof the magnetic recording portion with a second predetermined level, thesecond predetermined level being lower than the first predeterminedlevel; and the first comparison being given higher priority than thesecond comparison.
 2. An apparatus according to claim 1, wherein thejudger makes a judgment of:the first case when scan signals are in afirst condition of being above the first predetermined level over aspecified number of continuous blocks; the third case when scan signalsare in a second condition of being below the first predetermined leveland above the second predetermined level over a specified number ofcontinuous blocks; and the second case when scan signals are in theother condition.
 3. An apparatus according to claim 1, wherein the firstpredetermined level is a threshold value for judging whether scansignals are in connection with magnetic data, and the secondpredetermined level is a threshold value for judging whether scansignals are in connection with noise.
 4. An apparatus according to claim1, which is a camera.